Abstract: The dataset of the environmental geological survey on a scale of 1∶50 000 in the Longmen Map Sheet, Hainan Province in 2017 (also referred to as the Dataset) contains the survey information, data of hydrogeological boreholes, groundwater sampling information and the chemical component of the test results from the groundwater samples, which include 221 pumping (domestic) well points, 21 spring points, 7 surface water points, 10 hydrogeological boreholes, 808.77 m footage, and 56 groundwater full analysis sampling points. The data in the Dataset are credible since the survey points are consistent with applicable specifications, drilling quality is credible, the sampling conforms to relevant standards and the samples were tested in qualified labs. Therefore, the Dataset can faithfully reflect the hydrogeological and environmental geological conditions in the Longmen Map Sheet during the survey period. Furthermore, a backup groundwater source was delineated based on the survey results, making it possible to effectively alleviate the seasonal shortage of water and provide a basis for scientific and rational utilization of the groundwater resources.